[BC] Ground system

[Mike McCarthy]

I'm very cautious about driving electrodes too close to the tower pier.  
Depending on the foundation type, an electrode would need to clear the pad's perimeter or have provisions in place to go through the slab close to the tower.  This would be important for towers with bigger slabs.

In the case of a caisson, you'd prefer to see the primary earthing electrode(s) extend past the end of the concrete for fear of the foundation becoming a better ufer electrode.

In all cases, I create an 8 electrode ring at about a distance of 20-22ft from the tower center. This is the distance between 10ft. electrodes deemed to be best at maximizing coupling static/lightning energy to the earth. Each electrode is bonded by a radial strap from the tower and to each adjoining electrode. In effect creating a reverse funnel.  If the tower is especially tall or high powered, I'd increase the number of and extend the distance from the tower as needed except I'd likely start driving them deeper too.

In the case of plowing radials, I tend to plow them in first, then create the bonding ring, adding a 3-5" tension "S" in each wire to accommodate any settling or other movement of the wire.  I then bond to a minimum 2" strap, preferably 4".  I've seen too many installations where the radial wires snapped at the strap or ripped the strap due to excessive aged tension.

If the tower is high power, I'll install a 5 deg. pre-fabbed heavy screen (typically #6 wire on 6" center), then bond the radials to the edge of the screen.

MM